1. Field of the Invention
This invention relates to a novel process for producing retort packed tofu.
2. Description of the Prior Art
Since the development of a new coagulant glucono-delta-lactone (hereinafter referred to as GDL), a large-scale production of packed tofu has become possible. Because of the convenience in production and a shelf life of some lengths, this type of packed tofu has given rise to a new way of distribution for tofu. However, although suitable for the large-scale production, conventional processes do not produce sterile tofu capable of being stored for an extended period of time. In order to solve the problem, various processes have been proposed for the production of packed sterile tofu which can be stored for a prolonged period of time even at ambient temperatures. These processes for producing packed sterile tofu are broadly classified into two groups, the one group including those in which the sterilized soybean milk is aseptically packed in a container (aseptic packed tofu) and the other including those in which the packed soybean milk is finaly subjected to coagulation and sterilization by the heat treatment (retort packed tofu). The latter group of processes are superior to the former on account of easier operation and lower investment.
The retort packed tofu, however, has its own disadvantages resulting from the heat treatment at high temperaures, such as syneresis during the treatment, a specific disagreeable flavor, discoloration, and deteriorration in taste and textrure. As to the phenomenon of syneresis it has been attempted, for example, to use an anti-syneresis agent [Japanese Patent Application "Kokai" (Laid-open) No. 95,152/76] or to carry out preliminary heating at high temperatures before the retort treatment (Japanese Patent Publication No. 50,941/81). For other problems of discoloration, disagreeable flavor, and deterioration in taste and texture, there has been made none of proposals for their solution.